There is a need for optical cells that can contain a liquid or gas sample for many types of optical measurements. These optical cells have been made through many methods that include complete fabrication using glass walls, quartz walls, laser cut channels in optically clear materials, and micro-fabricated cells using polymeric materials.
In addition to simple optical cells, there is also a need for flow cells that allow for fluid to be passed through the cell during optical analysis. Such flow cells can be made in similar fashion as described above.
Beyond the simple cells above (both flowing and non-flowing), it is also desirable to create optical cells that can support acoustic standing waves across one or more dimensions of the cell. Such cells must be made of materials that have a large acoustic impedance difference relative to the solution within the cell. Effectively, this means that the walls of the flow cell must be constructed from a rigid material such as glass, silicon, or a metal, all of which have a large acoustic impedance mismatch with the typical aqueous solutions used in optical measurements. Current methods of such optical cell construction have relied upon capillary devices or channels created in silicon or glass (via etching or laser cutting). Once constructed, these acoustic cells allow the particles within the cell to be manipulated using the acoustic standing wave while an optical measurement is made.